Software Design Of The Multifunctional High-speed Data Acquisition Based On USB

With the development of computer and measurement technology, there are various data terminal based on kinds of interface on market. Currently high speed data acquisition device with multi-function based on the ISA or PCI built-in interface can achieve, but it is too large to carry. Although the collector based on the serial or parallel port is small, its function is single. Besides the development of software in PC could only use text programming language VC or VB etc leading to the cycle of development long and cost high. These have limited data terminal applications. Therefore a parallel data acquisition system of convenience and multi-function is presented in this paper based on USB2.0 interface using VC++ multithreading, LABVIEW virtual instrument technology. The main work is as follows:(l)With the advantage of convenience, it still can realize high speed data acquisition software design scheme with multi-function. We raise a plan to control high-speed A/D acquisition of two independent channel with CY7C68013A chips that integrated USB2.0 interface and the 8051 nuclear microprocessor. On the base of the hardware with the function as the signal disposal, power supply of the sensor and the balance of channel, I use KEIL C51 to develop USB firmware program, proposing PingPang BUFFER reconstruction mechanism and cooperate with FLASH, it realizes three modes of acquisition and the data storage management. We use LABVIEW to design the user interface combined with the VC++multithreading realizing efficient transmission. In brief we complete the software system of portable data acquisition with multi-function.(2) According to the development of USB firmware program, we make an agreement of many endpoints configuration and transfer protocol, Settings EP2 for command receiving, EP6 for command return, EP8 for data sending based on the endpoint configuration scheme. Through the independent operation to the port, we can guarantee the reliability of command transmission, the speed of data transmission, and synchronous operation. To realize the three function of acquisition:transient acquisition, real-time acquisition and off-line acquisition, we use two separate BUFFER to get the length of 500K per channel in transient and off-line mode. Furthermore we put forward an idea of bad block identifying to FLASH data storage to avoid data loss in the off-line mode to ensure the stable and reliable of data storage. In the real-time mode we achieve indefinite length of data acquisition based on PingPang BUFFER reconstruction.(3) In the design of friendly user interface we use a graphical interface development environment LABVIEW for platform and combined with VC++6.0. Using LABVIEW virtual instrument technology, through the graph to achieve the playback of history waveform, realizing dynamic display of the real-time data using chart, completed reconfigurable instrument function. We also use the LABVIEW event structure to ensure the respond to the user operation, the state machine structure to control in different modes. For the control of acquisition, we use multithreading mechanism to solve the contradiction between the high-speed of acquisition and waveform display in real-time, Including main receiving thread, we reset a special thread to receive and save data from USB interface, which reached the separation of data saving and display under the maximum rate of 100 KHz.(4)To test the function of the system, we use a signal generator to generate analog signals of different frequency and amplitude to detect the realization of parameter Settings, data acquisition and waveform display. We adopt PCI-GPIB card to control the signal generator and digital multimeter with GPIB interface so as to realize the calibration which guarantees the system’s precision. The tests show that the system has the advantages of multi-function and high-speed of data acquisition, reaching 0.3% of the system precision.